1. Field of the Invention
The present invention relates to a pressure vessel adapted to charge various kinds of pressurized substances, typical examples of which include various kinds of compressed gases such as CNG (compressed natural gas) and various kinds of liquefied gases such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas).
2. Description of Related Art
The pressure vessel adapted to charge various kinds of pressurized substances such as CNG is generally provided with a tubular main body, a metallic mouth ring which is attached to the tubular main body, and a valve which is attached to the metallic mouth ring. In general, an inner peripheral surface of the main body is composed of a liner portion composed of resin, and an outer peripheral surface of the liner portion is composed of a reinforcing portion of a high strength resin (such as FRP, etc.). A flange part is formed around one end of the metallic mouth ring so as to project outwardly. The liner portion covers a bottom surface of the flange part (that is a surface of the flange, which is positioned on an interior side with respect to an axial direction of the main body), and an upper surface of the flange part (that is a surface of the flange, which is positioned on an exterior side with respect to the axial direction of the main body).
In the conventional pressure vessel, one part of the liner portion, which is adapted to cover the bottom surface of the flange part (hereinafter, will be referred to as “flange seal part”) has been brought into close contact with the flange part with an internal pressure of a tank. Namely, when the interior of the pressure vessel is charged with a pressurized substance, the flange seal part is pressed on the bottom surface of the flange part with a pressure of the pressurized substance (internal pressure of the tank). Consequently, the flange seal part closely contacts the flange part. However, when the charging amount of the pressurized substance is small (namely, when the internal pressure of the tank is small), there have occurred cases where the flange seal part is not strongly pressed on the bottom surface of the flange part. Therefore, it has been required to improve the sealing properties furthermore. Under these circumstances, there has been proposed the technique of sealing the mouth ring with the liner portion while restraining the variations in the attaching position of the flange seal part relative to the flange part (See publication of unexamined Japanese patent application No. 2004-211783, for example).
As shown in FIG. 6, in the pressure vessel disclosed in the above publication, a control member 500 with high strength is provided outwardly of a flange seal part 510. The control member 500 is composed of a resin material with high strength, such as FRP, and serves to secure the flange seal part 510 in position from the outer peripheral side thereof. Therefore, in accordance with the pressure vessel disclosed in the above-described publication, it has been considered that the attaching position of the flange seal part 510 can be prevented from varying outwardly, and even when the internal pressure of the tank is small, variations in the attaching position of the flange seal part 510 relative to the bottom surface of a flange part 521 can be restrained, whereby a mouth ring 2 is sealed with a liner portion 511.
However, the pressure vessel disclosed in the above-described publication, which requires the control member, has exhibited the problem that the manufacturing person hour increases to raise the manufacturing costs.